BIOCHEMICAL COMPOSITION OF COTTON LEAVES AND THEIR CHEMICAL DEFOLIATION AS AFFECTED BY ENVIRONMENT

Abstract

The susceptibility of cotton plants to chemical defoliation was found to be greatly influenced by the soil moisture supply, soil fertility level, and fruiting load. Reducing sugar, non-reducing sugar, starch and dextrin, hemicellulose, total N, soluble and colloidal N content of the cotton leaves were detd. The starch and dextrin content revealed the greatest degree of covariance with an inverse relationship to the amt. of defoliation obtained. The coefficient of determination (r2) for the total covariance revealed that 61.31% of the variation in defoliation could be accounted for by the concomitant variation in starch content of the leaves. Although the total N content within the leaves revealed a high positive correlation with defoliation, a multiple correlation considering starch, total N and defoliation failed to account for a greater proportion of the variance in defoliation. Also, when starch is considered with reducing and non-reducing sugars, colloidal or soluble N, there was no improvement in accounting for the variance in defoliation over the simple relation of starch alone. It is concluded that it may be possible to predict, with fair accuracy, the susceptibility of a cotton field to chemical defoliation by making an assay of the starch content of the plants.